1. Field of the Invention
The present invention relates to a method for production and apparatus for production of an adhesive wafer which use a die attach film to transfer an adhesive for die bonding to the back surface of a wafer at the time of production of semiconductor devices.
2. Description of the Related Art
When die bonding semiconductor chips to substrates, lead frames, etc., the practice has been to coat the back surface of the wafer with an adhesive at the stage of the semiconductor wafer, dice the wafer, then die bond the individual semiconductor chips to the substrates or lead frames by the adhesive. One of the methods conventionally used for coating the back surface of a wafer by an adhesive is the method of attaching a die attach film to the back surface of the wafer and transferring the adhesive from the die attach film to the wafer. As shown in FIG. 6, a die attach film 10 is comprised of a long separation film 11 and an adhesive 12 formed in a layer on one surface of the separation film 11 and generally is provided in a form wound up in a roll.
The conventional method for coating the back surface of a wafer with an adhesive using a die attach film was to attach the die attach film 10 on the back surface of the wafer, move a cutter along the outer circumference of the wafer to cut the die attach film to match with the outer shape of the wafer, then peel off the separation film and reheat to cure the adhesive. Note that another method consisted of attaching a die attach film cut to the outer shape of a wafer in advance on to the back surface of the wafer and transferring the adhesive from the die attach film to the wafer.
Summarizing the problems to be solved by the invention, with the method of moving a cutter to cut the die attach film along the outer circumference of the wafer, the wafer was liable to end up being cut along with the die attach film or the wafer to end up being scratched. In particular, recent wafers are being formed thinner along with the reduction in size of semiconductor chips, so scratches or fractures occur more easily due to cutters. Further, the adhesive is being required to be coated over the entire back surface of the wafer without protruding from the wafer and without any uncoated parts. Accordingly, with the method of using a die attach film cut to the outer shape of the wafer in advance, it is necessary to position the wafer and die attach film with a high precision. The process and apparatus therefore end up becoming complicated.